Patent GB-917825-A (GB)
Title: Improvements in data storage apparatus
IPC: G06F11/16
Filed: 1959-11-16
Abstract: 917,825. Digital data storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Nov. 16, 1959 [Nov. 14, 1958 (2)], No. 38844/59. Class 106 (1). A digital data storage apparatus has means for moving a transducer to one of a plurality of tracks in response to particular address information, whereupon the address of the track read by the transducer is compared with the address information; if non-comparison is obtained, the transducer is directed to a different track and a further attempt to locate the required track is made. The apparatus is preferably a random access disc store of the kind described in Specification 857,284. The complete store comprises ten storage units each comprising fifty discs 55 (Fig. 3) rotating as a single shaft 56. Associated with each storage unit are three sets of transducers 59 supported from arms 58, one transducer of each set being upper or lower face of a disc. An address word is stored in a distributer 34 (Fig. 2) and occupies digit positions D1 to D6: DO defines the storage unit, D4 and D5 the face of the disc, D3 and D2 the track, of which there are one hundred to each face of the disc, and D1 the set of transducers to be used. Each track of a disc stores sixty ten-digit-plus-sign words with a two-word gap, the digits being recorded by the NRZ method in a two-out-of-five code serial by bit. A core buffer store contains sixty words recorded in parallel by bit and serial by digit. Positioning of transducer (Figs. 2a, 2b, 3).- After the address has been placed in the distributer, a seek instruction operates to drive a distributer read-out ring 88. After translation from the biquinary to two-out-of-five code, the lines 94 are marked at successive times by the address digits. The transducer unit and storage unit is determined by marking one of the thirty output lines from a 3 X 10 thyratron matrix 98 and the disc face and track by the setting of each row of a 4Î5 thyratron matrix 99. D1  selects one row of matrix 98, the digits D2 to D5 cause two out of the five thyratrons in each row of matrix 99 to conduct by coincidence of signals from ring 88 and lines 94. Finally, D6 selects one column of matrix 98 to mark one output line and operate one of a set of relays R107. This closes contacts 111 associated with the conductive thyratons of matrix 99 and sets up certain relays in trees 112, 113 (Fig. 3). These operate to determine null points on resistors 129, 132 which control the positioning of transducer arm 58. The disc address also determines which of the two transducers 58 is used by operating either relay R147 or R148. Additionally set are address relay contacts 118a which if the correct relays have been set operate relay R121. Further, if only one of the thirty contacts associated with the lines from matrix 98 is closed R122 operates extinguising the thyratrons. When the null point on each of resistors 129 and 133 has been located, a position found relay PF is operated by relays DN and TN. Write in of data from core storage (Figs. 5a to 5d).-After the seek operation has been performed, a write operation code is placed in OP register 29. This results in reaelection of the same address and if the same relays are set signal issues from OP register to a " locafier " unit 250 which operates a write check latch 217. When the first bit, a space bit, after the twoword gap in the selected track passes the transducer it switches in a compare circuit 79 and the following address digits of the track are compared with the address values stored in the relay contacts 118a (Fig. 2b). If a valid comparison is made a write mode latch 171 is turned on which sets a write gap latch 172 causing the transducer to erase the track for a space of four words under the control of a fourstage gap ring 188 stepped by a digit ring 156. At the end of four words an end write gap signal on line 201 turns off latch 172 which turns on write record latch 202. The four digit address of the track is then written and the contents of the core store 36 are stepped out to a parallelserial translator 205 and written on the track. The core store is of the kind in which a word is immediately re-written after read out. The last bit of the sixteenth word results in simultaneous end of ring signals from bit, digit and word rings to AND unit 215, the output tuning off write record latch 202 which turns on write check latch 217. The newly written track is then read and compared digit by digit, after passing through serial-to-parallel translator 73, with the contents of store 36 in compare unit 79. The bit signals are inverted at 231 and should there be concidence at AND units, e.g. 208 in the compare unit 79, an error signal issues on line 234 which turns on the write mode latch 171 to initiate a second write operation. The error-rewrite sequence may continue until an operator intervenes. Should an error be recognised at the first comparison of the required track address with the address at which the transducer is stationed the signal on line 234 prevents latch 171 from being turned on and causes a recycle relay RR (not shown) to operate. This sets the relay tree at an address removed ten places from the required address and when the relays DN and TN pick (Fig. 3), due to the transducer reaching the new address, relay RR drops out causing the original address to be operative. A new attempt is then made to find the original address. Read out to core storage.-A read operation code causes first a check of the track address with that of the required address as for a write operation. A valid compare operation turns on read latches 236 and the contents of the track are read through the serial-to-parallel translator to the core storage. Specifications 710,554, 748,996, 800,273, 819,789, 836,198 and 837,560 also are referred to.